Delta factor can displace sigma factor from Bacillus subtilis RNA polymerase holoenzyme and regulate its initiation activity

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Abstract
Summary A protein with a molecular weight of 21,000 daltons is found associated with a fraction of Bacillus subtilis RNA polymerase core. This protein (δ) does not react with antibody made against sigma factor and has a peptide map which is significantly different from sigma factor. At ratios of 2:1 to 4:1 (δ:holoenzyme) the δ displaces sigma factor completely from the core and associates in a 1:1 ratio with core to form δ-core. Under the same incubation conditions sigma factor at a ratio of 10:1 (sigma factor: δ-core) does not displace δ from the δ-core. The δ-core has much less activity as compared to holoenzyme on various DNA templates. However, sigma factor does stimulate the activity of δ-core enzyme under conditions of RNA synthesis. These observations and the results of others suggest that δ-core enzyme binds initially to specific DNA sites followed by δ release from the core-DNA complex and that the sigma factor binds to the core-DNA complex to initiate RNA synthesis. Thus both δ and sigma factors are required in a sequential fashion for specific transcription to occur in B. subtilis.